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Full text of "The Flow Of Gases In Furnaces"

APPENDIX X

HEAT CAPACITY AND CALORIFIC INTENSITY CURVES
BY A. D. WILLIAMS
HEAT is probably the energy of the moving molecules of a
substance. Its intensity is measured by the thermometric scale,
and its quantity by the Calorie or the British thermal unit. Heat
transfer takes place by conduction, convection or radiation and
will occur whenever a temperature differential exists. Fuel is
merely latent heat energy. The quantity of heat stored in a unit              !
of fuel may be determined by the calorimeter or computed from              \
the chemical composition of the fuel.    But the amount of heat              1
stored up within the fuel does not supply any index of the tern-              j
perature differential which may be established by its combustion.               !
For instance, blue water gas at 300 B.t.u per cubic foot will
produce a higher temperature than natural gas of three times this
thermal value or producer gas of one-half its thermal value, while
all of these fuels may be used in a suitably designed furnace for
the melting of steel or for other high-temperature applications.
Combustion is the oxidation of fuel, releasing the latent heat
and establishing a temperature differential which will permit
utilization of the heat. The losses which occur in combustion are
small and comparatively unimportant in comparison with the
enormous losses which occur in the application and utilization
of the heat released. At the same time fuel costs are continually
advancing. This leads to a consideration of the possibility of
substituting for one fuel another, or of introducing methods of
operation and apparatus, which will accomplish the result at a
lower cost.
Comparison of the relative values of different fuels for any
given purpose involves many factors, any one of which may have a
determinative effect. There are many tables giving the thermal